Numerical Investigation of Buoyancy Effect on Mixed Convection Heat Transfer Deterioration of Supercritical Pressure Carbon Dioxide

2017 ◽  
Author(s):  
Guoli Tang ◽  
Zhouhang Li ◽  
Yuxin Wu ◽  
Qing Liu ◽  
Junfu Lyu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Mixed Convection ◽  
Pipe Flow ◽  
Convection Heat Transfer ◽  
Supercritical Pressure ◽  
Convection Heat ◽  
Temperature Peak ◽  
Heat Transfer Deterioration ◽  
Mixed Convection Heat Transfer

For supercritical pressure fluid upward pipe flow, turbulent mixed convection heat transfer deterioration, which is generally considered to be caused by buoyancy, is often put a deep concern for safety issues. The deterioration is typically characterized by a localized wall temperature peak. Sometimes, there will be another moderate temperature peak after the first one. However, due to the lack of reliable measure method, the understanding of the flow structure for these two localized temperature peaks were still limited. In order to investigate the detailed mechanism for these two peaks and further understand the effect of buoyancy, a numerical study of supercritical pressure carbon dioxide pipe flow mixed convection heat transfer deterioration was conducted in this paper. The SST k-omega model was selected as turbulence model. A variable turbulent Prandtl number model was adopted in the study to improve simulation accuracy. The variation of flow field and turbulence behavior were carefully analyzed. The results show that, the localized wall temperature rise is due to the suppressed turbulence in the near wall region. For the first localized temperature peak, the suppressed turbulence is due to the acceleration of near wall fluid. While for the second one, the restrained turbulence is due to the acceleration of core flow fluid.

Simulation of mixed convection heat transfer to carbon dioxide at supercritical pressure

2004 ◽  
Vol 218 (11) ◽  
pp. 1281-1296 ◽  
Author(s):  
S He ◽  
W S Kim ◽  
P X Jiang ◽  
J D Jackson
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Carbon Dioxide ◽  
Mixed Convection ◽  
Convection Heat Transfer ◽  
Turbulence Models ◽  
Supercritical Pressure ◽  
Convection Heat ◽  
Computational Simulations ◽  
Mixed Convection Heat Transfer

Computational simulations of turbulent mixed convection heat transfer experiments using carbon dioxide at supercritical pressure have been performed by solving the Reynolds averaged transport equations using an elliptic formulation. A number of two-equation low Reynolds number turbulence models have been used and the results have been compared directly with the experimental data. It has been shown that most of the models were to some extent able to reproduce the effects of the very strong influences of buoyancy on heat transfer in these experiments. However, the performance of the models varied significantly from one to another in terms of the predicted onset of such effects.

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